def solve(n, k, num, taro, jiro, memo):
    if num >= n:
        if taro > jiro:
            memo[n][(taro, jiro)] = 1
            return 1
        else:
            memo[n][(taro, jiro)] = 0
            return 0
    if (taro, jiro) in memo[num]:
        return memo[num][(taro, jiro)]

    res = 0
    if num < k:
        for i in range(4, 7):
            for j in range(1, 7):
                res += solve(n, k, num + 1, taro + i, jiro + j, memo)
        res *= 2
    else:
        for i in range(1, 7):
            for j in range(1, 7):
                res += solve(n, k, num + 1, taro + i, jiro + j, memo)
    memo[num][(taro, jiro)] = res
    return res

n = int(input())
k = int(input())

memo = [{} for x in range(n + 1)]
win = solve(n, k, 0, 0, 0, memo)
res = win / 6**n / 6**n

print(res)